Self propelled and tractor driven combines are used to harvest small grains, beans, corn and like crops. The combines function to separate the grains from plant materials, such as straw, chaff, and other plants that are cut by the combine. The straw and chaff along with the other materials are discharged through a open back end of the combine into windrows on the ground and stubble behind the combine. Straw choppers having horizontal rotating drums carrying a plurality of knives have been attached to the rear combine to cut up the straw and spread the straw onto the ground behind the combine. The drums are belt driven and use substantial amounts of power to cut the straw. The chaff flows through the straw cutters into generally narrow rows behind the combine. One or more vertically rotating straw spreaders have been mounted on the back of combines to spread straw. These cutters use a single disk to distribute the straw. The chaff flows out of the combine into relatively narrow rows on the ground. This concentration of chaff results in rows of small particulate materials and uneven chemicals on the ground.